82 NEW YORK STATE MUSEUM 



Magnesite MgCOo 



Magnesite, the carbonate of magnesium, contains 52.4$ carbon 

 dioxid and 47.6$ magnesia. 



Ebombobedral crystals of magnesite are rare. It occurs 

 commonly in granular, cleavable or compact earthy masses and 

 as veins in serpentine. The luster is dull, sometimes vitreous 

 or silky, and the color white, 3 T ellowish or grayish white and 

 sometimes brown. 



Magnesite is commonly associated with serpentine, talc, 

 brucite and other magnesium minerals. Much of the marble 

 known as verd antique is composed of serpentine veined with 

 magnesite. It is found in Quebec, Pennsylvania, Maryland and 

 in several places in California and Massachusetts. It has been 

 found in the serpentine rocks of Westchester county, N. Y. 



Magnesite is used as a refractory material for the lining of 

 converters, etc.; also in the manufacture of epsom salts and 

 carbon dioxid for soda water. 



Siderite (spathic iron ore) FeCOj 



Siderite is the iron protocarbonate and contains 37.9$ carbon 

 dioxid and 62.1$ iron protoxid (a composition equivalent to 48.2$ 

 iron). Manganese, magnesium or calcium may also be present 

 in small quantities. 



Siderite is rhombohedral in crystallization, the crystals being 

 commonly rhombohedral in habit with curved faces resembling 

 those of dolomite. It is characterized in massive varieties by 

 the oblique rhombohedral cleavage common to this group of 

 carbonates. In color siderite is mostly grayish yellow or 

 brown, ranging from pale buff shades to dark brown or black. 

 The luster is vitreous to pearly and the mineral in general 

 resembles dolomite but is somewhat heavier and in most 

 instances is distinguished by its brown color. 



Massive siderite is often formed by the action of decaying 

 vegetable matter on limonite. It occurs in gneiss, mica and clay 

 slate and as clay iron stone in coal formations. It is found 

 abundantly in Cornwall and other English localities; also in the 

 coal formations of Pennsylvania, Ohio, Virginia and Tennessee, 

 at Hudson and Burden, Columbia co. and at Antwerp, Jefferson 

 co. N.Y. 1 Siderite supplies a little over 1$ of American iron ore. 



J N. Y. state rnns. Bui. 7. 18S9. 



